1. Field of the Invention
The present invention relates to a push switch used in input operation units of electronic apparatuses.
2. Background Art
As a switch for a signal of an input operation unit of an electronic apparatus, a push switch in which a movable contact operates with a click feeling by pressing is used. FIG. 7 is a sectional view of a conventional push switch. FIG. 8 is an external perspective view of the conventional push switch. FIG. 9 is an exploded perspective view of the conventional push switch. Case 1 is formed in a box shape having an opening at the upper surface and has a concave portion. Case 1 is formed of an insulating resin. Center contact 2 and outer contacts 3 are fixed to the inner bottom surface of the concave portion of case 1. Terminal 2A coupled to center contact 2 and terminal 3A coupled to outer contact 3 are extended toward the outside of case 1, respectively.
Movable contact 4 is formed of an elastic thin metal plate and formed in an upwardly convex dome shape. The lower end of the outer periphery of movable contact 4 is placed on outer contacts 3. Movable contact 4 is disposed in the concave portion. A lower surface of a top of the dome shape of movable contact 4 and center contact 2 face each other with a space therebetween.
Protective sheet 5 is an insulating film. Adhesive layer 5A is formed on the entire surface of the lower surface of protective sheet 5. Case 1 has wall part 1A on the periphery thereof. Protective sheet 5 is adhesively held on the upper surface of wall part 1A by adhesive layer 5A so as to cover the concave portion of case 1.
Next, an operation of a conventional push switch is described. A pressing force is applied to the top of the dome shape of movable contact 4 from the upper side via protective sheet 5. When the pressing force exceeds a predetermined force, the center portion of the dome shape is elastically reversed in a downwardly convex shape with a click feeling, so that the lower surface of the center portion of movable contact 4 is brought into contact with center contact 2. Thus, center contact 2 and outer contacts 3 are electrically conducting with each other via movable contact 4, so that a switch is turned on.
Then, when the applied pressing force is removed, the center portion of the dome shape of movable contact 4 elastically returns to an original upwardly convex shape with a click feeling. As a result, the center portion of movable contact 4 is apart from center contact 2, so that center contact 2 and outer contacts 3 are insulated from each other. Thus, a switch is returned to an OFF state.